The present invention relates generally to alarm systems for protection of property, and more particularly to such a system for sounding an alarm such as the horn of a vehicle, when the vehicle is tampered with.
In the preferred form of the invention hereinafter described in detail, there is provided circuitry comprising an electrical system powered by the battery of a vehicle for sounding the vehicle's horn, either immediately upon the opening of the hood or trunk of the vehicle, or following a time delay of about 15 seconds after opening one of the doors or subjecting the vehicle to motion, such as tilting or shaking it. The circuitry includes means for stopping the alarm after a predetermined period, which may be about 25 seconds. The circuit is not armed until the end of a predetermined interval, about one minute, after the user has turned off the ignition. This provides ample time for the user and passengers to leave the vehicle and close the doors before the system is armed. The circuitry includes a master switch by which to disable the system, as when the vehicle is to be driven by someone not familiar with the system, such as an attendant in a garage or parking lot.
It is accordingly the principal object of the invention to disclose a novel alarm system for use in protecting a vehicle. Other objects and purposes are to provide such a system which, when armed, sounds an alarm immediately upon the occurrence of certain kinds of tampering such as opening of the hood or trunk, and sounds an alarm at the end of a predetermined time interval after the occurrence of other kinds of tampering such as opening a door of the vehicle or shaking or otherwise moving the vehicle; to provide, in such a system, means for stopping the sounding of the alarm after a length of time sufficient to frighten away a would-be thief; to provide such a system which is in unarmed condition as long as the ignition switch is on and for about one minute after that switch is turned off; to provide such a system including a master switch for disabling the system when desired; and for additional objects and purposes as will be understood from a reading of the following description of a preferred embodiment of the invention taken in connection with the accompanying drawings.